(1) Field of the Invention
The present invention relates to detergents and rinse aids for machine dishwashing. The invention relates, in particular, to detergents and rinse aids for machine dishwashing and to supply forms which provide detergents and rinse aids in one product and comprise certain polymers. These compositions are summarized below under the generic term “detergents for machine dishwashing” or “machine dishwasher detergents.”
At present, the demands made on machine-washed dishware are frequently higher than on manually washed dishware. For instance, even dishware which has been completely cleaned of food residue will not be evaluated as impeccable when, after machine dishwashing, it still has whitish marks which are based on water hardness or other mineral salts and stem from dried-on water drops owing to lack of wetting agent.
In order to obtain sparkling and mark-free dishware, rinse aids are, therefore, used with success at present. The addition of rinse aid at the end of the washing program ensures that the water runs off substantially fully from the ware, so that the different surfaces are residue-free and flawlessly shiny at the end of the wash program.
Machine cleaning of dishware in domestic machine dishwashers typically includes a prewash cycle, a main wash cycle and a rinse cycle, which are intermitted by intermediate rinse cycles. In most machines, the prewash cycle for heavily soiled dishware can be actuated, but is only selected by the consumer in exceptional cases, so that a main wash cycle, an intermediate rinse cycle with clean water and a rinse cycle are carried out in most machines. The temperature of the main wash cycle varies, depending on the machine type and program level selection, between 40 and 65° C. In the rinse cycle, rinse aids, which typically comprise nonionic surfactants as the main constituent, are added from a dosing tank in the machine. Such rinse aids are present in liquid form and have been widely described in the prior art. Their task consists principally in preventing lime spots and films on the cleaned dishware. In addition to water and low-foaming nonionic surfactants, these rinse aids often also comprise hydrotropes, pH modifiers such as citric acid or scale-inhibiting polymers.
(2) Description of Related Art, Including Information Disclosed Under 37 C.F.R. §§ 1.97 and 1.98.
EP-B1 0 197 434 (Henkel) discloses liquid rinse aids which comprise mixed ethers as nonionic surfactants. In the machine dishwasher, a multitude of different materials (glass, metal, silver, plastic, porcelain) is cleaned. This variety of materials has to be wetted as well as possible in the rinse cycle. Rinse aid formulations which comprise exclusively mixed ethers as the surfactant component fulfill these requirements only to a slight extent, if at all, so that the rinse or drying effect is not satisfactory, especially in the case of plastic surfaces.
The reservoir tank in the machine dishwasher has to be replenished with rinse aid at regular intervals, one filling being sufficient for from 10 to 50 rinse cycles depending on the machine type. When refilling of the tank is forgotten, glasses, in particular, become visually unappealing as a result of lime spots and films. Therefore, in the prior art there exist some proposed solutions to the problem of integrating a rinse aid into the detergent for machine dishwashing. These proposed solutions are tied to the supply form of the compact tablet.
For instance, European patent application EP-A-0 851 024 (Unilever) describes two-layer detergent tablets whose first layer comprises peroxy bleaches, builders and enzyme, while the second layer comprises acidifier and a continuous medium with a melting point between 55 and 70° C., and also scale inhibitors. The high-melting continuous medium is intended to retard the release of the acid(s) and scale inhibitor(s) and bring about a rinse aid effect. There is no mention in this document of pulverulent machine dishwasher detergents or surfactant-containing rinse aid systems.
It was an object of the present invention to provide novel rinse aids which, with regard to the performance properties, provide at least the same results as rinse aids common on the market and which additionally bring further performance advantages. The novel rinse aids should be usable both as conventional rinse aids and in the form of combination products, and should develop their advantageous properties irrespective of their formulation form. Not least, the use of the novel rinse aids should also be possible in conventional detergents for machine dishwashing, i.e. the compositions should also bring performance advantages as an additive component.